Geological Society of America

T141 Rocks from Space! Using Meteorites to Understand the Physical, Chemical, and Mineralogical Evolution of Planetary Bodies

Wednesday, 28 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

RECONSTRUCTING LUNAR METEORITE THERMAL HISTORIES WITH 40AR/39AR THERMOCHRONOLOGY

Paper number: T141-15
Program: Technical Sessions
Time: 4:40 PM – 4:50 PM

Authors

Marissa Tremblay Presenting Author
Purdue University, West Lafayette, IN
Darren F. Mark
Scottish Universities Environmental Research Centre, East Kilbride, Scotland
Darren F. Mark
University of St Andrews, St Andrews
John N. Carter
Scottish Universities Environmental Research Centre, East Kilbride, Scotland
Simon Mason
Purdue University, West Lafayette, IN
Abigail Robinson
Institut de Physique du Globe de Paris, Paris
Peter Chung
University of Glasgow, Glasgow

Abstract

Much of our knowledge about the evolution of the Moon’s surface comes from geochemical studies of Apollo samples. In particular, the application of the ⁴⁰Ar/³⁹Ar system to Apollo samples has formed the backbone of our understanding of the Moon’s bombardment through time. However, the existing body of lunar ⁴⁰Ar/³⁹Ar datasets are biased, in that the Apollo missions sampled a small fraction of the lunar surface. Moreover, the framework in which many existing lunar ⁴⁰Ar/³⁹Ar datasets have been interpreted is overly simplistic and does not account for the complex thermal histories that many lunar samples demonstrably experienced. To address these issues, we conducted detailed, temperature-controlled ⁴⁰Ar/³⁹Ar measurements on more than a dozen lunar meteorites that, based on a comparison of their bulk elemental composition to remote sensing data, likely sample regions of the Moon’s surface outside of the Apollo mission landing sites. The ⁴⁰Ar/³⁹Ar analyses were conducted on individual lithic or impact melt clasts or impact melt regions identified in each sample from initial characterization using scanning electron microscopy. We will present ⁴⁰Ar/³⁹Ar step-heating datasets from a subset of the meteorites studied, and interpret these datasets using (1) Bayesian, nonparametric multiple diffusion domain models that account for Ar diffusion from multiple K-bearing phases, and (2) forward models that predict the entire ⁴⁰Ar/³⁹Ar age spectrum as a function of a sample’s geologic and subsequent laboratory thermal histories. These new ⁴⁰Ar/³⁹Ar datasets and interpretations will contribute to a more complete representation of the lunar crust’s thermal evolution and therefore inform outstanding debates about the Moon’s early impact history that rely heavily on existing ⁴⁰Ar/³⁹Ar datasets from Apollo samples.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-359588

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